Thermal transport properties of gold-covered thin-film silicon dioxide

Due to continued miniaturization, the performance and reliability of electronic devices composed of multiple thin layers of material are highly dependent on effective thermal management. Since the thermal properties of thin films, such as SiO₂, can vary considerably from bulk values, the determination of those properties (as well as the interface resistance between SiO₂ and adjacent layers) is critical for the purposes of design. In this work, a transient thermo-reflectance system has been employed to measure the thermal characteristics of thin-film SiO₂ layers. Results show that for layers of SiO₂ in the range of 100-1000 Å, the intrinsic thermal conductivity (TC) is independent of thickness and smaller than the traditionally reported value of bulk silicon dioxide (1.4 W/m-K). The intrinsic value was measured to be around 90% (1.27 W/m-k) and 75% (1.05 W/m-k) of the latter bulk value for thermally grown (TG) and ion beam sputtered (IBS) oxides, respectively. The thermal interface resistances of TG and IBS SiO₂ films were measured at 1.68 × 10^-8 m²-K/W and 2.58 × 10^-8 m²-K/W, respectively. If a chromium film of around 100 Å is deposited between the gold and SiO₂ layers, the interface thermal resistance improves to 0.78 × 10^-8 m²-K/W for TG films and 1.15 × 10^-8 m²-K/W for IBS films. Thus, the effective thermal resistance of SiO₂ thin-films (i.e., with interface effects) is up to one order of magnitude smaller than the values reported for bulk SiO₂.